Electric circuit breaker having improved operating means



Nov. 28, 1967 J. H. LEONARD 3,355,685

ELECTRIC CIRCUIT BREAKER HAVING IMPROVED OPERATING MEANS Filed Sept. 50, 1966 7 Sheets- Sheet 1 If) ("M41 62a 58 52 uvvnvmm JAMES H. LEONARD G Q 9, y

I Hfis Nov. 28, 1967 J. H. LEONARD ELECTRIC CIRCUIT BREAKER HAVING IMPROVED OPERATING MEANS Filed Sept. 30, 1966 wm $3 mm Nqv. 28, 1967 J. H. LEONARD 3,355,685

ELECTRIC CIRCUIT BREAKER HAVING IMPROVED OPERATING MEANS Filed Sept. 30, 1966 7 Sheets-Sheet 5 J. H. LEONARD Nov. 28, 1967 ELECTRIC CIRCUIT BREAKER HAVING IMPROVED OPERATING MEANS '7 Sheets-Sheet 5 Filed Sept. 30, 1966 lNl/E/VTOR. JAMES H.LEO/V.4/?D

(ii/2 M Raf- Nov. 28, 1967 J. H. LEONARD 3,355,685

ELECTRIC CIRCUIT BREAKER HAVING IMPROVED OPERATING MEANS Filed Sept. 30, 1966 7 Sheets-Sheet 6 56 //0 200 JAMES/1. LEONARD By @ou/ Nov. 28, 1967 J. H. LEONARD ELECTRIC CIRCUIT BREAKER HAVING IMPROVED OPERATING MEANS '7 Sheets-Sheet '7 Filed Sept. 30, 1966 Hi-P United States Patent 3,355,685 ELECTRIC CIRCUIT BREAKER HAVING IMPROVED OPERATING MEANS James H. Leonard, Cedar Rapids, Iowa, assignor to Square D Company, Park Ridge, III., a corporation of Michigan Filed Sept. 30, 1966, Ser. No. 583,193 9 Claims. (Cl. 335-8) This invention relates to multipole electric circuit breakers of the molded-case type.

It is desirable to provide molded-case circuit breakers of higher current-carrying capacity and current-interrupting ability'than heretofore considered possible in circuit breakers of that type without exceeding certain maximum dimensions for the case. To accomplish these results, it is necessary that the current-carrying parts and contact pressures be relatively large, and that adequate Venting be provided for the arc gases. The circuit breaker of this invention provides the desired larger current-carrying capacity and current-interrupting ability in a case of relatively small size by including an improved mounting means for the movable contact arms, an improved latching means for a releasably latchable trip lever of the operating mechanism, an improved magnetic tripping means cooperable with the latching means, an improved mounting means for a common trip bar, and an improved venting means.

Accordingly, an object of this invention is to provide a molded-case circuit breaker of relatively large currentcarrying capacity and interrupting rating having a case of relatively small size.

Another object is to provide an electric circuit breaker having improved mounting means for a movable contact arm. 7

Another object is to provide an electric circuit breaker having improved magnetic tripping means.

A further object is to provide a multipole electric circuit breaker having an improved single adjusting means for adjusting the air gaps in the magnetic circuits of the magnetic tripping means of all the poles.

Still another object is to provide an electric circuit breaker having an improved latching means for a releasably latchable trip lever of the operating mechanism.

A still further object is to provide a multipole electric circuit breaker having improved mounting means for a common trip bar.

Yet another object is to provide an electric circuit breaker having improved venting means.

Other objects and advantages will appear when the following specification is considered along with the accompanying drawings, in which:

FIG. 1 is a front view of a circuit breaker constructed in accordance with the invention;

FIG. 2 is a side view of the circuit breaker of FIG. 1;

FIG. 3 is an enlarged sectional view taken generally along the line 3-3 of FIG. 1, the operating parts of the circuit breaker being shown in ON position;

FIG. 4 is an enlarged sectional view taken generally along the line 4-4 of FIG. 2, a cover, a handle, and a shield of the circuit breaker being removed and the remainder of the operating parts being shown in ON position; FIG. 5 is an enlarged view, partially in section, taken from the top of FIG. 1;

FIG. 6 is a sectional view taken generally along the line 6-6 of FIG. 3, certain parts being omitted forclarity;

FIGS. 7, 8, and 9 respectively are front, side, and end views of the operating mechanism assembly of the circuit 3,355,685 Patented Nov. 28, 1967 breaker of FIG. 1 showing the assembly before it is installed in the casing;

FIG. 10 is a fragmentary sectional view taken generally along the line 10-10 of FIG. 4;

FIG. 11 is a fragmentary sectional view taken generally along the line 11-11 of FIG. 10;

FIG. 12 is a fragmentary sectional view taken generally along the line 12-12 of FIG. 4, but including the handle of the circuit breaker;

FIG. 13 is a fragmentary sectional view taken generally along the line 13-13 of FIG. 4; and

FIG. 14 is a fragmentary sectional view taken generally along the line 14-14 of FIG. 4.

A three-pole molded-case circuit breaker 20 constructed in accordance with the invention is shown in FIGS. 1 and 2. The case of the circuit breaker 20 includes a base 22, a main cover 24, and a' pair of oppositely disposed terminal covers 25 each removably secured to the cover 24 by a pair of screws 26 in a manner best shown in FIG. 5. Each screw 26 is provided with a captive washer 27 to retain the screw 26 in assembled relationship with the respective terminal cover 25 when the terminal cover 25 is removed from the cover 24.

The case of the circuit breaker 20 is divided generally into three compartments or pole spaces 28, 29, and 30 (FIG. 6), one for each of the three poles of the circuit breaker. To this end, the base 22 is provided with a pair of opposed parallel side walls 22a and 22b and a pair of spaced intermediate walls 220 and 22d parallel to the side walls 22a and 22b, and the cover 24 is provided with corresponding pairs of side walls 24a and 24b and intermediate walls 240 and 24d. The opposite end portions of the walls 24a, 24b, 24c, and 24d are recessed for reception of the terminal covers 25.

Each of the intermediate walls 240 and 24a is provided adjacent opposite ends respectively with a pair of expansion-type inserts 32, one of which is shown in FIG. 5. The screws 26 are threaded respectively into the inserts 32 to secure the terminal covers 25 to the cover 24.

A pair of alignment pins 34 are provided between the base 22 and cover 24, the pins 34 being shown respectively adjacent the left-hand ends of the Walls 22c and 22d as viewed in FIG. 4. After alignment of the base 22 and cover 24 by the pins 34, the base 22 and cover 24 are riveted together by four hollow rivets 36 in a manner best shown in FIG. 5, two of the rivets 36 being disposed respectively adjacent opposite ends of the walls 22c and 240, and two of the rivets 36 being disposed respectively adjacent opposite ends of the walls 22d and 24d. In each of the walls 24c and 24d, the two inserts 32 are spaced farther apart than the two rivets 36.

Within the base 22, opposite ends of the compartments 28, 29, and 30 are defined respectively by pairs of transverse walls 22e and 227, 22g and 22h, and 22 and 22k (FIGS. 3 and 4). Within the cover 24, opposite ends of the compartments 28, 29, and 30 are defined respectively by pairs of transverse walls corresponding to the pairs of walls 22e and 221, 22g and 22h, and 22 and 22k of the base 22, a pair of transverse walls 24g and 24h being shown in FIG. 3 and transverse walls 24], 24h and 24k being visible in FIGS. 5 and 6, the transverse walls of the cover 24 corresponding to the walls 22e and 22 of the base 22 not being shown;

As best shown in FIG. 3, adjacent the right-hand end of the circuit breaker 20 as viewed therein, the center compartment 29 is provided with a terminal strap 38 secured to the base 22 by a screw 40. The terminal strap 38 extends through the transverse wall 22h defining the compartment 29, an inner end portion within the compartment 29 being provided with a stationary contact 42 3 and an arc runner 4-4 and an outer end portion having a connector body 46 secured thereto by a screw 48. The connector body 46 is provided with an aperture for receiving an electrical conductor or conductors (not shown), and is provided with two clamping screws 50;

Adjacent the left hand end of the circuit breaker 20' as viewed in- FIG. 3, the'center compartment 29 provided with a terminal strap 52 secured to'the base 22 by means of a hollow bolt 4 hereinafter more fully described and by means of a screw 56 shown in FIG. 12. The terminal strap" 52 extends through the transverse Wall 22g defining the compartment 29,- an outer end ortion having a connector body 46 carrying two clamping screws 50" secured thereto by a screw 48'; the screw 48; connector body 46, and clamping screws 50' oo'nnected to the terminal strap 52- being identical to those connected to the terminal strap 38. The terminal strap 52 is thinner than the terminalsnap- 3'8; in order that its resistance will be greater and more heat will be generated therein by flow of e'ledt rical current therethr'ough. However, a metallic plate 58' is secured to the outer end portion of the terminal' strap 52 to provide additionat thread engagement with the respective screw 48.

discernible from FIGS; 4 and 5, the two outer cornpartrhents 28* and 30' are also each rovidedwith a terminal strap 38 identicalto the terminal strap 38 of the center compartment 2?, it being under-sto'od that eachof the terminal straps 38 ofthe two outer compartments also is secured to the base 22 by a screw 40', has a stationary contact 42 and an arc runner 44 secured thereto; and has a connector body 46 carr ing two clamping screws 50 secured thereto by a serew 48, these parts being idendeal to the screw 40', stationary cont-act 4-2, are runner 44',- conneotor body 46", screw 48,- andclamping screws 50"connected' to the terminal strap-38 ofthe center compartment 2-9.

Asdisce'rnible from FIGSa- 4 and 6, thetwo supercompartments 28 and 30 are also each provided with a terminalstrap 52- identicalto the terminal strap 52 or the center compartment-29, it being understood that eaeh or the terminal straps 52- of the two outer" compartments also is secured to the base 22 by a hollow bolt 54 and a screw 56, is provided with a' plate" 5-8,- and has a connector body 46- carrying two clamping. screws 50 secured thereto by a screw 48', these parts being identieal to the hollow bolt 54 screw 56, plate 58',- cohnector body 46, screw 48, and clamping screws 50 cofinected to" the terminal strap 52 of the" centercorripartment 29.

FIGS. 7,- 8, and 9 show an operating mechanism assembly 60 of the circuit breaker- 20 before the assembly 60 is mounted on the base 22', the movable parts being shown inthe equivalent of tripped posit-ion, an'd FIGS. 3, 4, and 12 show the operating. mechanism assembly 60 mountedon the base 22, with the movable parts in position.

Theoperating mechanism assembly 60 (FIGS: 73-. 8, and 9) includes the three terminal straps 52 and plates 58 for the three compartments 28,-. 29, and 301 Further, a pair of frame members 62 are provided, the frame members ezeach havingacu-rled end portion- 6221 (FlGS 7 and 9)- opposite a hooked end portion 621: (FIG; 8 As shown in; FIGS. 3' and the frame mendhers 62 are respectively secured to the base 22- in the ceh'ter compartment 2-9 by a pair ofscrews 64 provided respectiyel y with a pair of nuts 65', the hooked end portions 62b hooking respectively beneatha pair ofpro jections (not shown) disposed inthe compartment 29 respectively on the intermediate walls- 22cand 22d.

Each of the frame members 62 is provided with a stub airle- 66. A pair of handle arm members 68 are pivotally mounted respectivelyon the stub axles 66, the portions of the members 68 adjacent the aides 66 being outwardly other so as to straddle the frame members 62. The handl'e" arm members 68 are connected by a pair of pins 70. A handle 72 formed of i'risulating material includes a portion which projects through an aperture 24m in the cover 24, as best shown in FIG. 3. A shield 74 is provided on the handle 72 to cover any portion of the aperture 24m not covered by the handle 72 in any position thereof. Within the casing of the circuit breaker 20, the handle 72 is formed to embrace one of the pins 70, as shown in FIG. 12. The handle 72 includes a pair of depending portions 72a (FIGS: 3 and 14) by which it is secured to the handle arm members 68, a pair of screws 76 extending respectively through the depending portions 7242 being threaded respectively into a pair of holes 78 (FIG. 8) provided respectively in the handle arm members 68.

An upper spring" anchor 80* is supported on the handle arm members 68 and has one end portion of a tension spring 82 connected thereto. The other end portionof the spring 82 is connected to' a lower spring anchor 84 in which a toggle pin 86" is pivotally mounted (FIGS. 9 and 12).-

Each frame member, 62- is also provided with a stub axle 88- for the mounting ot a trip lever assembly,- the triplever assembly including a pair of trip lever members 90 pivotally mounted adjacent oneendrespectively onthe stub axles 88 and connected adjacent the other end by apin 91- provided with a bushing 92-.

Each trip lever member 99 is provided centrally thereofwith a stub axle or rivet 94 (FIG. 12). A- pair of upper links 96 are pivotal-1y mounted adjacent one end respec tively on the rivets 94-, only onelink 96 being shown in FIG. 12. The opposite end portions of the toggle pin- 86 are pi-votally mounted respectively in the upper links 96 adjacent the other ends thereof. A pair of lower links 93 arepivotally mounted adjacent one end respectively on the opposite end portions of the toggle pin- 86-, only one link 98 heingqshownin FIG-.- 1-2.- The oppositeend portions of a drive pin I00 are pivotal-1y mounted respectively in the links 98= adjacent the other ends thereof.-

The trip lever members 90 are normally held in a latched position by a generally U-shaped first latch mornber 102 spaced leg portions of which are pivot-ally mounted on a pin 194- having opposite end portions mounted respectively in the frame members 62. In the latched position of the trip lever members 90; the bushing 92 on the pin 91 engages arecess1-02a (FIG. 8) on one of the leg portions of-the first latch member 102,- as c-an be seen in FIG. The first latch member 102 is Biased clockwise, as viewed in FIGS. 3 and 8-, by a tor= sion spring 166 mounted on the pin 1-04.

Each frame member 62 is also provided with a stub axle 1'03 (FIGS. 3: and 12). A pairof spaced side portions of a generally channel-shaped contact arm carrier 110 are pivotally mounted adjacent one end'l of the carrier' 116" respectively on the stub axles 108.- The drive pin passes through the side port-ions oi? the carrier generally dent-rally thereofL-Adjacent its free end, the carrier 11'0 earries a generally rectangular crossbar 1-12 formed of insulating. materialLAs shown in FIGS'. 3; and 12, the transverse portion of the carrier 110 adjacent the free end thereof is bent at filler through ninety degrees oppositely from the side portions, and is staked toan Is-shaped bracket 114, it beingunderstood that a short leg of the bracket- 114 opposite the bent portion 110d is also staked to the transverse portion of the carrier 110. Thus, the Crossbar 112 is clamped ontwo adjacent sides respectively by the transverse portion of the carrier 1 10 and the bent portion 110a, and on the other twoadjacent s'ides respeetiveiy by the two leg portions ofthe bracket 114. I

Each of the two outer compartments 28 and 50 is provided with a contact arm carrier I16 (FIGS. 4 7 8, and 9') similar to the carrier 110 but while the carrier 110 is" pivoted on the stub axles 108 and driven by the drive pin 160, the carriers 116 are driven by the crossbar 112' and are not mounted on any stub axles such as.

the stub axles 19 8', but merely rock against the base 22.

Each of the outer compartments 28 and 30 is also provided with a bracket 118 similar to the bracket 114 and secured to its respective carrier 116 about an end portion of the crossbar 112 in a similar manner to that in which the bracket 114 is secured to the carrier 110.

Each of the compartments 28, 29, and 30 is provided with an elongated movable contact arm 120 having a movable contact 122 secured thereto and having a bent end portion 120a adjacent the movable contact 122, the movable contact 122 cooperating with the respective stationary contact 42 and the end portion 120a cooperating With the respective arc runner 44, as best shown in FIG. 3. Further, each movable contact arm 120 is provided with a pair of studs 124 and 126 spaced longitudinally of the contact arm and having a pair of sleeved nuts 128 and 130 threaded respectively thereon, a compression spring 132 surrounding the stud 124 and bearing at one end against the nut 128 and at the other end against the transverse portion of the respective carrier 110 or 116, and a compression spring 134 surrounding the stud 126 and bearing at one end against the respective bracket 114 or 118 and at the other end against the contact arm 120.

The crossbar 112 is provided With a pair of shields 136 received respectively in recesses in the walls 22c and 22d. In each of the compartments 28, 29, and 30, the crossbar 112 and the associated carrier 110 and bracket 114 or carrier 116 and bracket 118 are drilled and tapped to receive a round-headed screw 138 against the head of which the respective contact arm 120 seats (FIG. 12). Each screw 138 is adjustably locked in position by a nut 140, the adjustment of the screw 138 determining the position of the respective contact arm 120 and compensating for manufacturing variations.

Adjustment of each nut 128 on its stud 124 controls the angular position of the respective contact arm 120 with respect to the crossbar 112 and also the amount of pressure between the contact arm 120 and the head of its respective screw 138. Adjustment of each nut 130 on its stud 126 controls the amount of angular motionof its respective contact arm 120 between the open and closed positions thereof, the amount of overtravel of the operating mechanism after the contact arm 120 reaches closed position, and the amount of contact pressure between the movable contact 122 on the contact arm 120 and the respective stationary contact 42. a Each of the compartments 28, 29, and 30 is provided with an arc stack including a plurality of arc plates 142 and a generally L-shaped arc shield 144 one leg portion of which lies generally parallel to and adjacent the respec tive wall 24 24h, or 24k of the cover 24 and is perforated. Each of the walls 24 24k, and 24k is provided with a pair of holes 24p, and each of the terminal covers 25 is provided with three vents 25a (FIGS. 3 and 5). Arc gases may escape through the right-hand terminal cover 25 as viewed in FIG. 3, the vents 25a in the other terminal cover not being used. In addition, each of the side walls 22a and 22b is provided with a vent hole 22n, one such vent hole being shown in the side wall 22a in FIG. 2.

Each of the terminal straps 52 has a bimetallic strip member 146 secured to an inner end portion thereof, the base of each bimetallic strip member being connected to the respective contact arm 120 by a set of flexible cables 148. l

A trip'bar 150 extends through the center compartment 29 and into each of the outer compartments 28 and 30, as shown in FIGS. 4 and 6. Each of the walls 22c and 22d is recessed to receive a pivot pin 152 on which the trip bar 150 is pivotally mounted. As best shown in FIGS. and 11, the trip bar 150 is provided with appropriate V-shaped notches 150a in which opposite end portions of the pivot pins 152 are respectively received to pivotally support the trip bar. As an aid in assembling, each pivot pin 152 is provided with a central collar por- 6 tion to anchor the pivot pin in place in the respective wall 220 or 22d before the trip bar is mounted.

As best shown in FIG. 3, the trip bar 150 is provided with a second latch member in the form of a roller 154 mounted on a pin 156. The roller 154 normally engages a notch 102a (FIG. 8) in one of the leg portions of the first latch member 102 to maintain the first latch member 102 in latched position. As will be understood, opposite end portions of the pin 156 are retained in an appropriate slot in the trip bar 150 by means of a retaining plate 158 secured to the trip bar 150 by a screw 160. The trip bar 150 is normally biased clockwise as viewed in FIG. 3 by means of a tension spring 162 having one end portion hooked on the trip bar 150 and the other end portion secured to the base 22 by means of a screw 164 (FIG. 6).

The trip bar 150 is provided with three upstanding lever portions 150b, one in each of the compartments 28, 29, and 30. Each of the portions 15% has a screw 166 adjustably threaded therethrough and lockable in an adjusted position by a nut 168.

The trip bar 150 is provided with three appropriate slots, one in each of the compartments 28, 29, and 30, in which three'armature rods 170 are received. Each armature rod 170 is reciprocably mounted adjacent one end in a respective one of the hollow bolts 54, as best shown in FIG. 13, and has a round actuating nut 172 adjustably threaded on the other end portion. Each armature rod 170 also has an armature 174 in the form of a flat plate fixedly secured thereto generally centrally thereof.

Each hollow bolt 54 extends through a respective one of the terminal straps 52 and a respective portion of the base 22 and is threaded into the bight portion of a generally U-shaped magnetic core member 176 to secure both the terminal strap 52 and the magnetic core member 176 to the base 22. Each armature 174 is biased away from its respective core member 176 by a compression spring 178 disposed between the armature 174 and the respective terminal strap 52.

An improved single adjusting means for simultaneously adjusting the air gap between the three armatures 174 and their respective core members 176 is provided. Thus, an arcuately shaped control member 180 (FIGS. 1, 3, and 6) is disposed in the cover 24 and retained therein by a retaining member 182 which defines an arcuate groove for the control member 180 with the cover. The control member 180 is provided with an inwardly extending projection 180a which is received in a bent portion 184a (FIGS. 3, 4, and 13) of a lever 184 disposed in the center compartment 29. The control member 180 is also provided with a slot 180k accessible through an aperture in the retaining member 182 for the reception of a screwdriver (not shown) by which the control member may be shifted, the slot 1801; serving as a position indicating means.

The lever 184 is provided generally centrally thereof with a projecting pin 18% (FIG. 3) which is received in a slot in a crossbar 186 shiftably mounted in the walls 220 and 22d. A pin 184a projecting oppositely to the pin 184b is provided adjacent the end of the lever 184 opposite the bent portion 184a and is received in a recess in the wall 22g, as best shown in FIG. 6.

Each of the outer compartments 28 and 30 is provided with a'lever 188 having a projecting pin 1881) (FIG. 13) disposed adjacent one end and received in a slot in the crossbar 186 and an oppositely projecting pin 188c disposed adjacent the other end and received in a recess in the respective wall 22e or 22 The lever 184 is provided with a bent portion 184d (FIG. 3) and each of the levers 188 is provided with a similar bent portion 188d (FIGS. 4 and 13) in which an actuating screw 190 is adjustably locked by a nut 192.

A counterbalancing compression spring 194 (FIGS. 4 and 6) is provided adjacent one end of the crossbar 186 to balance the effect of the armature springs 178 thereon.

7 Three retaining members 196 (FIGS. 3, 6, and 13) are secured respectively under the heads of the hollow bolts 54 and have portions in engagement respectively with the inner end portions of the levers 184 or 188 to retain the respective pins 184C or 1880 in the recesses in the respective walls 226, 22g, or 221'. Various recesses in the side of the base 22 opposite the cover 24 are sealed by a pair of insulation plates 198 and 2001 Shifting of the control member 180 by means such as a screwdriver pivots the lever 184 about the pin 184a and also shifts the crossbar 186 to pivot the levers 188 respectively about the pins 1880; The pivoting of the levers 184 and 188 moves the actuating screws 190 toward or away from the respective core members17'6 to either move the respective arm-ature's 174 closer to their respective core members 176 or allow the armatures 174 tobe moved farther from their respective core members 176 under the influence of their respective springs 17 8. v

Upon the sustained flow of a moderate overload current through any one of the poles of the circuit breaker 20, the respective bimetallic strip member 146 flexes to move the respective screw 166 and rotate the trip bar150 counterclockwise as viewed in FIG. 3. Upon the flow of a severe overload or fault current through any one of the poles of the circuit breaker 20, the respective armature 174 is attracted into engagement with its respective core memher 176 against the force of the respective spring 178, shifting the respective armature rod 170 and rotating the trip bar 150 counterclockwise as viewed in- FIG. 3 by means of the respective not 172. Such rotation of the trip bar 150' moves the roller 154 out of latching relationship with the latch member 102, whereby the trip lever members 90 are released to move the axis of the rivets 94 (FIG. 12) to the opposite side of the line of action of the spring 82 and effect collapsing of the toggle links 9'6 and 98 to pivot the movable contact arms 1201c OPEN or OFF position. The contact arms 120 may also be moved to OPEN or OFF position by operation of the handle 72 to move the line of action of the spring 82 to the opposite side of the axis of the rivets 94.

I claim:

1-. An electric circuit breaker comprising an elongated molded case including a base and a covers'ecured together and each having a pair of spaced parallel outer side walls and an intermediate wall disposed generally parallel to and spaced from said outer side walls, whereby said case is providedwith a pair of side-by-side elongated compartments, a pair of stationary contacts secured to said base and disposed respectively in said compartments, a pair of pivotable contact arm carriers disposed respectively in said compartments, afirst crossbar disposed in said case and extending transversely of said compartments, a pair of brackets secured respectively to said carriers, each of said brackets securing a portion of said crossbar to its associated carrier whereby said carriers are pivotable as a unit, a'pair of mounting screws adjustably mounted respectively in said carrierabrackets, and the respective portions of said first crossbar, each of said mounting screws having a rounded head portion on the opposite side of its associated carrier from said cover, a pair of elongated movable contact arms respectively associated with said carriers, each of said contact arms having a pair of studs extending from one side thereof and spaced longitudinally therealong, each of the studs having a nut adjustably threaded on a free end portion thereof, one of the studs of each contact armextending through the associated carrier and having a coil spring disposed thereon between its respective nut and the associated carrier, the other of the studs of each contact arm extending through the associated bracket and having a coil; spring disposed thereon between the contact arm and the associated bracket, each of said cont-act arms having a portion between its respective studs on said one side in seating engagement with the head of the mounting screw of the associated carrier and having a movable contact secured to the other side thereof and engageable with a respective one of said stationary con- 8, tacts, releasably latehable trip lever means pivotally mounted in one of said compartments, means in said one compartment connecting said trip l'ever means and the respective carrier in such a' manner that movement of said trip lever means causes movement of said carrier, said trip lever means being releasable from a latched position to effect separation of said movable contacts respectively from said stationary contacts, a pivot pin mounted in the intermediate wall of said base adjacent said cover and having opposite end portions extending respectively into said compartments, an elongated trip bar disposed in said' case and extending transversely of said compartments, said trip bar having a pair of portions respectively disposed on opposite sides of the intermediate wall of said base andrespectively cooperating with said opposite end portions of said pivot pin to pivotally mount said trip bar, latching means in said one compartment interposed between said trip lever means and said trip bar, said latching means normally being eltective to maintain said trip lever means in" a latched position, said latching means including a shiftably and rotatably mounted roller and said trip'bar being pivotable to effect shifting of said roller and release of said trip lever means, a pair of terminal straps each having an inner end portion disposed in a respective one ofsaid compartments, a pair of generally U-shaped magnetic core members each having a bight portion disposed outside a respective one of said compartments in spaced relationship to a respective one of said terminal straps on the opposite side thereof from said cover and each having a pair of spaced leg portions extending into arespective one of said compartments in straddling relationship to the respective terminal strap, said base including a pair of portions disposed respectively between said' bight portions ofsaid core' members and said terminal straps, a pair of hollow bolts extending respectively through said terminal straps, base portions, and the bight portions of said core members and respectively securing said terminal straps and core members to said base, a pair of armature rods disposed. respectively in said compartments, each armature rod being reciprocably mounted adjacent one end in a respective one of said hollow bolts, a pair of armature plates fixedly secured respectively to said armature rods generally centrally thereof, each of said armature plates normally being in spaced relationship to the free end portions-of the leg portions of a respective one of said core members, a pair of coil springs disposed respectively on said armature rods respectively between said terminal straps and said armature plates and biasing said armature plates respectively away from said core members, each of said armature plates being attractable toward its respective core member upon flow of severe overload current through the associated terminal strap, each of said armature rods extending through a portion of said trip bar and having actuating means adjacent the other end engageable with said trip bar to pivot said trip bar and efiect release of said trip lever means upon attraction of its associated armature plate toward the respective core member, and air gap adjusting means for simultaneously adjusting bothof the air gaps between said armature plates and their respective core members, said air gap adjusting means including a pair of levers pivotally' mounted adjacent one end respectively in said compartments, a pair of actuating means respectively carried by said levers and respectively engagiing said armature plates on the opposite sides thereof respectively from their biasing springs and respectively movable toward and away from the respective core members upon pivotal movement of said levers respectively in opposite directions, a second crossbar disposed in said case and extending transversely of said compartments, said second crossbar being shiftably mounted in the intermediate wall of said base, a control member shiftably mounted in said cover and accessible through an aperture therein, means connecting said control member and one of said levers in such a manner that shifting of said control member causes pivoting of said one lever, means connecting said one lever and said second crossbar in such a manner that pivoting of said one lever causes shifting of said second crossbar, and means connecting said second crossbar and the other of said levers in such a manner that shifting of said second crossbar causes pivoting of said other lever.

2. An electric circuit breaker as claimed in claim 1, including a second pair of terminal straps secured to said base and disposed adjacent an opposite end of said case from the first-mentioned pair of terminal straps, each terminal strap of said second pair having an inner end portion disposed in a respective one of said compartments and extending longitudinally of said case and having an outer end portion disposed outside the respective compartment, said stationary contacts being secured respectively to the inner end portions of said second pair of terminal straps, a pair of connector bodies secured respectively to the outer end portions of said second pair of terminal straps, each of said connector bodies having a conductor clamping screw threadedly mounted therein and accessible from the side of its associated terminal strap facing said cover, said base having a pair of transverse walls through which said second pair of terminal straps respectively extend and said cover having a corresponding pair of transverse walls, each of said compartments being partially defined by a respective one of the transverse walls of said base and a respective one of the transverse walls of said cover, the outer side walls and the intermediate wall of both said base and said cover projecting outward beyond said transverse walls longitudinally of said case, the projecting portions of the outer side walls and the intermediate wall of said cover being recessed at portions thereof remote from said base to provide a recess for a terminal cover, and a terminal cover secured to said cover in said recess, each of said transverse walls of said cover having a vent extending therethrough, and said terminal cover having a pair of vents extending therethrough and communicating respectively with the vents in said transverse walls of said cover.

3. An electric circuit breaker comprising a case, a stationary contact in said case, a contact arm carrier pivotally mounted in said case, a bracket secured to said carrier, a mounting screw adjustably mounted in said carrier and bracket, said mounting screw having a rounded head portion, an elongated movable contact arm having a pair of studs extending from one side thereof and spaced longitudinally therealong, each of said studs having a nut adjustably threaded on a free end portion thereof, one of said studs extending through said carrier and having a coil spring disposed thereon between its associated nut and said carrier, the other of said studs extending through said bracket and having a coil spring disposed thereon between said bracket and the contact arm, said contact arm having a portion between said studs on said one side in seating engagement with the head of said mounting screw and having a movable contact secured to the other side thereof and movable into and out of engagement with said stationary contact upon pivotal movement of said carrier respectively in opposite directions.

4. An electric circuit breaker comprising an elongated molded case including a base and a cover secured together and each having a pair of spaced parallel outer side walls and an intermediate wall disposed generally parallel to and spaced from said outer side walls, whereby said case is provided with a pair of side-by-side elongated compartments, a pair of stationary contacts secured to said base and disposed respectively in said compartments, a pair of movable contact arms pivotally mounted respectively in said compartments, a pair of movable contacts mounted respectively on said contact arms and movable into and out of engagement respectively with said stationary contacts upon pivotal movement of said contact arms respectively in opposite directions, means interconnecting said contact arms in such a manner that they pivot as a unit, releasably latchable trip lever means pivotally mounted in one of said compartments, means in said one compartment connecting said trip lever means and the contact arm in said one compartment in such a manner that movement of said trip lever means causes movement of said contact arm, said trip lever means being releasable from a latched position to effect separation of said movable contacts respectively from said stationary contacts, a pivot pin mounted in the intermediate Wall of said base adjacent said cover and having opposite end portions extending respectively into said compartments, an elongated trip bar disposed in said case and extending transversely of said compartments, said trip bar having a pair of portions disposed respectively on opposite sides of the intermediate wall of said base and cooperating respectively with said opposite end portions of said pivot pin to pivotally mount said trip bar, said trip bar normally being etfective to maintain said trip lever means in said latched position and being pivotable to efiect release of said trip lever means, and a pair of tripping means dis posed respectively in said compartments, each of said tripping means being operative to pivot said trip bar upon the flow of an overload current through the contacts in its respective compartment.

5. An electric circuit breaker comprising an elongated molded case, a stationary contact disposed in said case, a movable contact arm pivotally mounted in said case, a movable contact mounted on said contact arm and movable into and out of engagement with said stationary contact upon pivotal movement of said contact arm respectively in opposite directions, releasably latchable trip lever means pivotally mounted in said case, means in said case connecting said trip lever means and said contact arm in such a manner that movement of said trip lever means causes movement of said contact arm, said trip lever means being releasable from a latched position to effect separation of said contacts, an elongated trip bar pivotally mounted in said case, latching means in said case interposed between said trip lever means and said trip bar, said latching means normally being effective to maintain said trip lever means in said latched position, said latching means including a shiftably and rotatably mounted roller and said trip bar being pivotable to effect shifting of said roller and release of said trip lever means, and tripping means in said case, said tripping means being operative to pivot said trip bar upon the flow of an overload current through said contacts.

6. An electric circuit breaker as claimed in claim 5, wherein said roller is mounted on said trip bar.

7. An electric circuit breaker comprising an elongated molded case including a base and a cover secured together, a stationary contact disposed in said case, a movable contact arm pivotally mounted in said case, a movable contact mounted on said contact arm and movable into and out of engagement with said stationary contact upon pivotal movement of said contact arm respectively in opposite directions, releasably latchable trip lever means pivotally mounted in said case, means in said case connecting said trip lever means and said contact arm in such a manner that movement of said trip lever means causes movement of said contact arm, said tn'p lever means being releasable from a latched position to effect separation of said contacts, an elongated trip bar pivotally mounted in said case, said trip bar normally being eifective to maintain said trip lever means in said latched position and being pivotable to effect release of said trip lever means, a terminal strap having an inner end portion disposed in said case, a generally U-shaped magnetic core member having a bight portion disposed in spaced relationship to said terminal strap on the opposite side thereof from said cover and having a pair of spaced leg portions straddling said terminal strap, said base including a portion disposed between said terminal strap and said bight portion of said core member, a hollow bolt extending through said terminal strap, base portion, and the bight portion of said core member and securing said terminal strap and core member to said base, an armature rod disposed in said case and reciprocably mounted adjacent one end in said hollow bolt, and an armature plate fixedly secured to said armature rod generally centrally thereof, said armature plate normally being spaced from the free end portions of the leg portions of said core member and being attractable toward said core member upon flow of a severe overload current through said terminal strap, said armature rod extending through a portion of said trip bar and having actuating means adjacent the other end engageable with said trip bar to pivot said trip bar and eifect release of said trip lever means upon attraction of said armature plate toward said core memher.

-8. An electric circuit breaker comprising an elongated molded case having a pair of side-by-side elongated compartments, a pair of stationary contacts disposed respectively in said compartments, a pair of movable contact arms pivotally mounted respectively in said compartments, a pair of movable contacts mounted respectively on said contact arms and movable into and out of engagement respectively with said stationary contacts upon pivotal movement of said contact arms respectively in opposite directions, means interconnecting said contact arms in such a manner that they pivot as a unit, releasably latchable trip lever means pivotally mounted in one of said compartments, means in said one compartment connecting said trip lever means and the contact arm in said one compartment in such a manner that movement of said trip lever means causes movement of said contact arm, said trip lever means being releasable from a latched position to effect separation of said movable contacts respectively from said stationary contacts, an elongated trip bar pivotally mounted in said case and extending transversely of said compartments, said trip bar normally being effective to miantain said trip lever means in said latched position and being pivotable to eifect release of said trip lever means, a pair of terminal straps each having an inner end portion disposed in a respective one of said compartments, a pair of generally U-shaped magnetic core members each having a bight portion disposed generally parallel to a respective one of said terminal straps on the opposite side thereof from said trip bar and each having a pair of spaced leg portions straddling the respective one of said terminal straps, a pair of armature plates disposed respectively in said compartments respectively on the opposite sides of said terminal straps from the bight portions of said core members, each of said armature plates being biased away from and normally being spaced from the free end portions of the leg portions of a respective one of said core members and being attractable toward the respective core member upon flow of a severe overload current through the associated terminal strap, a pair of actuating means connected respectively to said armature plates, each of said actuating means being engageable with said trip bar to pivot said trip bar and effect release of said trip lever means upon attraction of its associated armature plate toward the respective core member, and air gap adjusting means for simultaneously adjusting both of the air gaps between said armature plates and their respective core members, said air gap adjusting means includin a pair of levers pivotally mounted adjacent one end respectively in said compartments, a pair of actuating means respectively carried by said levers and respectively engaging said armature plates on the opposite sides thereof respectively from their respective core members and respectively movable toward and away from the respective core members upon pivotal movement of said levers respectively in opposite directions, an elongated crossbar disposed in said case and extending transversely of said compartments, said crossbar being shiftably mounted for reciprocal movement longitudinally thereof, a control member shiftably mounted in said case and accessible through an aperture therein, means connecting said control member and one of said levers in such a manner that shifting of said control member causes pivoting of said one lever, means connecting said one lever and said crossbar in such a manner that pivoting of said one lever causes shifting of said crossbar, and means connecting said crossbar and the other of said levers in such a manner that shifting of said crossbar causes pivoting of said other lever.

9. An electric circuit breaker comprising an elongated molded case including a base member and a cover member secured together, each of said base and cover members having a pair of spaced parallel side walls and a transverse wall respectively aligned with. the side walls and the transverse wall of the other of said base and cover members, the side walls of said base and cover members projecting outwardly beyond said transverse walls longitudinally of said case, an elongated terminal strap secured to said base member and extending longitudinally of said case, said terminal strap having an inner end portion in said case and extending through the transverse wall of said base member and having an outer end portion disposed outwardly of said transverse walls longitudinally of said case, a stationary contact secured to said inner end portion of said terminal strap a movable contact in said case movable into and out of engagement with said stationary contact, a connector body secured to said outer end portion of said terminal strap, said connector body having a conductor clamping screw threadedly mounted therein and accessible from the side of said terminal strap facing said cover member, the portions of the side walls of said cover member projecting beyond said transverse walls being recessed at portions thereof remote from said base member to provide a recess for a terminal cover, and a terminal cover disposed in said recess and removably secured to said cover member, the transverse wall of said cover member having a vent therethrough, and said terminal cover having a vent extending therethrough and communicating with the vent in the transverse wall of said cover member.

References Cited UNITED STATES PATENTS 3,053,954 9/1962 Jenclts et al7 335l8 3,171,929 3/1965 Jencks et al. 200-1l6 3,171,939 3/1965 Jencks et al. 200144 3,181,041 4/1965 Falk 335176 BERNARD A. GILHEAIJY, Primary Examiner.

H, BROOME, Assistant Examiner. 

3. AN ELECTRIC CIRCUIT BREAKER COMPRISING A CASE, A STATIONARY CONTACT IN SAID CASE, A CONTACT ARM CARRIER PIVOTALLY MOUNTED IN SAID CASE, A BRACKET SECURED TO SAID CARRIER, A MOUNTING SCREW ADJUSTABLY MOUNTED IN SAID CARRIER AND BRACKET, SAID MOUNTING SCREW HAVING A ROUNDED HEAD PORTION, AN ELONGATED MOVABLE CONTACT ARM HAVING A PAIR OF STUDS EXTENDING FROM ONE SIDE THEREOF AND SPACED LONGITUDINALLY THEREALONG, EACH OF SAID STUDS HAVING A NUT ADJUSTABLY THREADED ON A FREE END PORTION THEREOF, ONE OF SAID STUDS EXTENDING THROUGH SAID CARRIER AND HAVING A COIL SPRING DISPOSED THEREON BETWEEN ITS ASSOCIATED NUT AND SAID CARRIER, THE OTHER OF SAID STUDS EXTENDING THROUGH SAID BRACKET AND HAVING A COIL SPRING DISPOSED THEREON BETWEEN SAID BRACKET AND THE CONTACT ARM, SAID CONTACT ARM HAVING A PORTION BETWEEN SAID STUDS ON SAID ONE SIDE IN SEATING ENGAGEMENT WITH THE HEAD OF SAID MOUNTING SCREW AND HAVING A MOVABLE CONTACT SECURED TO THE OTHER SIDE THEREOF AND MOVABLE INTO AND OUT OF ENGAGEMENT WITH SAID STATIONARY CONTACT UPON PIVOTAL MOVEMENT OF SAID CARRIER RESPECTIVELY IN OPPOSITE DIRECTIONS. 